Mylar sleeves are proven to be the best quality sleeves available, and are in use in museums worldwide including the Smithsonian. Most other commercially available currency sleeves are not made of Mylar, and contain PVCs that, over time, leach out of the plastic and into the notes, damaging them permanently.
There are no rules about what you can and cannot put in your safety deposit box.
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BWJM, F.O.N.A.
Life Member of CPMS, RCNA, ONA, ANA, IBNS, WCS.
President, IBNS Ontario Chapter.
Treasurer, Waterloo Coin Society.
Show Chair, Cambridge Coin Show.
Fellow of the Ontario Numismatic Association.